1. Field of the Invention
A method utilized in a wireless communication and related communication device are disclosed, and more particularly, to a method of handling system information reception with measurement gap configuration in a wireless communication system and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs).
In the LTE system, a user equipment (UE) applies a system information acquisition procedure to acquire system information broadcasted by an E-UTRAN upon selecting and upon re-selecting a cell, after handover completion, after entering the E-UTRAN from another radio access technology (RAT), upon receiving a notification that the system information has changed, or upon receiving an indication about the presence of an Earthquake and Tsunami Warning System (ETWS) notification, upon exceeding the maximum validity duration, etc. The system information includes most essential and most frequently transmitted parameters that are needed to acquire other information of a cell for connection establishment (e.g. call establishment).
On the other hand, the UE reports measurement information in accordance with the measurement configuration as provided by the E-UTRAN. The E-UTRAN provides the measurement configuration applicable for the UE in a radio resource control (RRC) connected state by means of dedicated signaling, i.e. using the RRCConnectionReconfiguration message. The measurement configuration includes parameters such as measurement objects, reporting configurations, measurement identities, quantity configurations and measurement gaps, wherein the measurement gaps are periods that the UE may use to perform measurements, i.e. no uplink and downlink transmissions are scheduled. The parameters of the measurement configuration have been defined in a RRC specification document 3GPP TS 36.331, so it is not given herein.
However, due to unclear specification for system information reception with measurement gap configuration in the LTE system, several scenarios are described as follows.
In the first scenario, the UE may receive a system information change notification from the network when the UE is in the RRC connected state and is configured with a measurement gap. Thus, a chance that reception of system information is intervened by the measurement gap may occur. However, the LTE system does not clearly define how the UE shall deal with this situation. In this situation, the UE may not perform system information reception due to the measurement gap. Thus, the UE may use previously received system information, thereby affecting UE performance.
In the second scenario, for important system informations (or “required”), e.g. MasterInformationBlock (MIB), SystemInformationBlockType1 (SIB1), SystemInformationBlockType2 (SIB2), (or SIB8 if code division multiple access (CDMA) 2000 is supported), if the reception of required system information is intervened by the measurement gap, the UE is not allowed to access the cell before these required system information are received. If the reception of a MIB is intervened, the UE needs to wait another 10 ms for the next MIB, 20 ms for SIB1, and for SIB2. Moreover, the UE may need to wait at least 80 ms depending on the system information periodicity (SI-periodicity). The actual delay may be the combination of above since more than one system information reception can be intervened, and thereby the total delay can be extremely long. In other words, the cell access may be delayed for a long time when the reception of the required system information is delayed. Thus, the UE may enter a RRC idle state, and release the connection.
In the third scenario, an eNB is responsible to configure measurement gaps for the UE. Due to a great number of UEs under the eNB, the eNB cannot schedule all UEs specific measurement gaps to avoid system information reception of the UE. In addition, scheduling of the measurement gaps for avoiding the system information reception for the UEs is a heavy burden for the eNB. Therefore, a collision between system information reception and measurement gap configuration occurs.